Due to numerous modifications, the technology for producing good quality multicomponent ingots from rare earth up to 15cm is perfected on a modified system F200, allowing obtaining fragments for two targets from one ingot.
Smelting is held in the arc discharge mode in a way that arc column is oriented and held along the axis with the help of an external magnetic field. This enables a significant amount of the radial current components in the alloy required for its effective mixing. Furthermore, to improve the mixing of the alloy and maintaining the flat surface of the ingot the alternating external magnetic field was used.
Arc energy parameters were selected and optimized experimentally based on two conditions: to ensure metals melting in the entire volume of the crystallizer and to avoid significant evaporation of fusible metals.
An inert gas was used as the working gas in the chamber with high thermal conductivity and low viscosity, which contributed to a uniform heat transfer across the entire surface of the alloy. To avoid arc mode change from a cord to a diffuse melting was conducted at an elevated atmospheric pressure.
An experimental vacuum-arc system F-200 has a sufficient potential of the power input: arc current of 1200-1300 A, voltage up to 100 V. A controlled gas composition at a pressure from 20 mm Hg to the atmosphere in the working chamber can be created. Melting was conducted in inert gases. Raw materials used were zirconium, yttrium, praziodium, hafnium, gadolinium, etc.
Obtained ingots of 150 mm in diameter are cut in an electroerosive way into fragments with dimensions of 110 x 100 x 8 mm. A composite target is composed of four of these fragments. In some cases the number of fragments is increased to six retaining the desired target size.
Figure. 1-3 show the upper end surface of the processed ingot #31 (height 13.5cm), as well as obtained targets in a package. Fig. 4-5 shows ingot #45 and the targets without packaging.
Obtained targets are used for applying coatings with low thermal conductivity to an aircraft turbine blade.